• Proceedings of the KSME Conference
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• 2005.11a
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• pp.223.1-223.1
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• 2005

• Journal of Advanced Marine Engineering and Technology
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• v.22 no.2
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• pp.200-209
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• 1998

Experiments have been conducted to determine heat transfer characteristics for a two-dimen-sional turbulent wall attaching offset jet at different oblique angles to a flat surface. The local Nusselt number distributions were measured using liquid crystal as a temperature sensor. Wall static pressure coefficient profiles were measured at the Reynolds number Re 53200(based on the nozzle width, D) the offset ratio H/D from 2.5 to 10 and the oblique angle a from $0^{\circ}$, to $40^{\circ}$ It is observed that the maximum Nusselt number point occurs slightly upstream of time-averaged reattachment point for all oblique angles. The correlations between the maximum Nusselt number and Reynolds number offset ration and oblique angle are presented.

• Korean Journal of Computational Design and Engineering
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• v.11 no.5
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• pp.375-383
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• 2006

Presented in this paper is a new fast and robust algorithm generating NC tool path for 2D pockets with islands. The input shapes are composed of line segments and circular arcs. The algorithm has two steps: creation of successive offset loops and linking the loops to a tool path. A modified pairwise technique is developed in order to speed up and stabilize the offset process, and the linking algorithm is focused on avoiding thin-wall cutting and minimizing tool retractions. The proposed algorithm has been implemented in C++ and some illustrative examples are presented to show the practical strength of the algorithm.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.5A
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• pp.423-431
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• 2011

In this paper, carrier frequency offset and 2-D AoA (Angle-of-Arrival) estimation methods are proposed for an OFDM-based MRS (Mobile Relay Station) with UCA (Uniform Circular Array). The proposed methods are performed by using the preamble symbol in downlink and can improve the performance of CFO estimation significantly, compared with the conventional method. The proposed methods can be divided into two methods (method 1 and method 2) depending on the order of the AoA estimation and CFO estimation. It is shown by computer simulation under Mobile WiMAX environments that the proposed methods can estimate the CFOs and AoAs of adjacent BSs effectively.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2012.05a
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• pp.441-442
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• 2012

• Journal of the Korean Society for Precision Engineering
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• v.25 no.3
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• pp.157-164
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• 2008

While developing physical prototype from CAD model, rapid prototyping mainly focuses on two key points reducing time and material consumption. So, we have to change from a traditional solid model to building a hollowed prototype. In this paper, a new method is presented to hollow out solid objects with uniform wall thickness to increase RP efficiency. To achieve uniform wall thickness, it is necessary to generate internal contour by slicing the offset model of an STL model. Due to many difficulties in this method, this paper proposes a new algorithm that computes internal contours computing offset model which is generated from external contour using wall thickness. Proposed method can easily compute the internal contour by slicing the offset surface defined by the sum of circle swept volumes of external contours without actual offset and the circle wept volumes. Internal contour existences are confirmed by using the external point. Presented algorithm uses the 2D geometric algorithm allowing RP implementation more efficient. Various examples have been tested with implementation of the algorithm, and some examples are presented for illustration.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.42 no.1
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• pp.105-110
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• 2005

In this paper, a new technique to reduce the phase noise in microwave oscillators is proposed using the resonant characteristics of the Photonic Bandgap(PBG). We applied PBG structure to ground of the microstrip line resonator with the low Q(Quality factor). Therefore, we improved about 10 dBc in contrast to phase noise characteristic of the conventional microstrip line oscillator at 2.4 GHz ＠ 100 MHz offset. Output power is 7.09 dBm.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.10
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• pp.3304-3312
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• 1996

An experimental study on the convective heat transfer characteristics was performed for a two-dimensional wall attaching offset jet(WAOJ). Thermochromic liquid crystal was used to measure the plate wall temperature. The Nusselt number was measured for Reynolds numbers from 6, 500 to 39, 000, and the offset ratios from 0.5 to 15. The maximum Nusselt number point coincides with the time-averaged reattachment point and Nusselt number decreases monotonically after the jet reattaches on the wall. In the recirculation region Nusselt number minimize near the upstream corner and then increases as X/D decreases to vanishes. This suggests the existence of secondary vortices, causing an additional mixing of the flow in the corner. The correlations between the local Nusselt number and Reynolds number, Re, offset ratio, H/D, and streamwise distance, X/D are presented.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.38 no.10
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• pp.754-764
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• 2001

Class A bipolar second-generation current conveyor (CCII) with low current-input impedance and its offset-compensated CCII for high-accuracy current-mode signal processing are proposed. The CCIIs consist of a regulated current-cell for current input, a emitter follower for voltage input, and a cascode current mirror lot current output. In these architecture, the two input stages are coupled by current mirror to reduce the current input impedance. Experiments show that the CCII has impedance of 8.4 Ω and offset voltage of 40 mV at current input terminal. To reduce this offset, the offset-compensated CCII adopts diode-connected npn and pnp transistor in the proposed CCII. Experiments show that the offset-compensated CCII has current input impedance of 2.1 Ω and offset voltage of 0.05 mV. The 3-dB cutoff frequency of the CCIIs when used as a voltage follower extends beyond 30 MHz. The power dissipation is 7.0 mW

• The Journal of the Acoustical Society of Korea
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• v.24 no.4E
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• pp.152-157
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• 2005

In this paper, a new data-aided joint phase and frequency estimator, which has very low computational complexity, is proposed and its variances of phase and frequency estimates are derived. To estimate the phase and frequency offset, first of all, the overall observation interval is divided into same length sub-intervals, and then phase estimates are independently computed based on symbols of the each sub-intervals. To be continue the sequence of computed phase estimates, proper integer multiples of $2{\pi}$ are added to (or subtracted from) the computed phase estimates, which is called linearized phase estimate. The phase offset of the proposed joint estimator is estimated by averaging the linearized phase estimates and the frequency offset by averaging the differences between consecutive linearized phase estimates. The variance of the proposed phase offset estimate is same to MCRB of phase if there is no frequency offset, but it is smaller than MCRB of phase if there is frequency offset. However, the variance of the proposed frequency offset estimate is bigger by at least 0.5 dB than MCRB of frequency with the same observation interval.